What is wrong with this statement? “The limiting reactant of a reaction is whichever reactant is present in a smaller amount.”

Question

Limiting Reactant Questions

Answer 1

The limiting reagent is present at less than the stoichiometric amount of moles. Which doesn't mean it's present at less moles or less mass.

 

Say for example you have the balanced reaction:

 

2 Al + 3 I₂ ------> 2 AlI₃

 

Now if Iodide were present at 2.5 mole and Aluminum at 2 mole. Iodide is the limiting reagent (even though I₂ mole > Al) because the reaction stoichiometry shows 3 Iodide per 2 Aluminum. So we have excess Al and I₂ will determine the amount of product formed.  I₂ is also heaver by AMU (253.88 grams per mole) than Al (26.981539 grams per mole).

Answer 2

This is wrong because it is not the amount of a reactant that determines if it is limiting or not, necessarily. A limiting reactant is the reactant that is used up when the reaction is completed. This can be based upon the coefficients in the chemical equations or moles or certain other factors